It makes a big difference if there are three or four of them. If there are three, then you're correct, and x = 2. You also correctly computed 2x-1, although your notation of using '.' for multiplication is not a good one for numbers. Use the asterisk: * for multiplication.

But i really don't know what would i ahve done if it was a bigger number..

It makes a big difference if there are three or four of them. If there are three, then you're correct, and x = 2. You also correctly computed 2x-1, although your notation of using '.' for multiplication is not a good one for numbers. Use the asterisk: * for multiplication.